老y万人敬仰。 @ 2018-05-04 18:21:55

#include<iostream>
using namespace std;
int main()
{
    long long k,n;
    cin>>k;
    for(int i=0;i<k;i++)
    {
        n+=i;
    }
    cout<<n<<endl;
}

by AThousandSuns @ 2018-05-04 18:28:06

额……你确定你看清了题目描述吗

by AThousandSuns @ 2018-05-04 18:28:21

@yangyibangyi

by 留守新手村 @ 2018-05-04 19:45:59

加油，你能看懂的

by lion0514 @ 2018-08-18 16:36:16

好像您@错人了@AThousandSuns

by lion0514 @ 2018-08-18 16:36:24

好像您@错人了 @ AThousandSuns

by lion0514 @ 2018-08-18 16:36:29

好像您@错人了 @AThousandSuns

by AThousandSuns @ 2018-08-18 21:41:38

@I_am_gone__ 并没有，你点进去看一看

by lion0514 @ 2018-08-19 07:13:35

您是怎么办到的？@AThousandSuns

by lixx @ 2018-10-01 09:03:09

金钱不是一天加一

by WAWA @ 2018-10-19 20:01:57

emmmmmmmmm